The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems for performing deposition and/or etching typically include a processing chamber with a pedestal. A substrate such as a semiconductor wafer may be arranged on the pedestal during processing. In chemical vapor deposition (CVD) or atomic layer deposition (ALD) processes, a gas mixture including one or more precursors may be introduced into the processing chamber to deposit film on the substrate or to etch the substrate. In some substrate processing systems, radio frequency (RF) plasma may be used to activate chemical reactions. CVD and ALD systems using plasma are called plasma-enhanced CVD (PECVD) and plasma-enhanced ALD (PEALD).
One consequence of almost any deposition process is that undesirable deposition occurs on interior surfaces of the processing chamber and creates film residue. The film residue can build up over time and may dissolve, detach or otherwise disperse in the processing chamber during substrate processing, which increases defects. To prevent this from occurring, the film residue is periodically removed using remote plasma clean (RPC) gas to avoid subsequent contamination.
Referring now to FIG. 1, a gas delivery assembly 10 is shown to include an elbow connector 20 having a body 21 defining a first gas channel 24 having an inlet and an outlet. The body 21 also defines a second gas channel 25 having an inlet and an outlet. The outlet of the first gas channel 24 is connected to a middle portion of the second gas channel 25 (at a junction 26). In use, gas such as vaporized precursor gas, purge gas and/or other gases flow from the inlet of the first gas channel 24 to the junction 26 and from the junction 26 through a lower portion of the second gas channel 25 (as shown by path 27) to a gas distribution device such as a showerhead (not shown).
The inlet of the second gas channel 25 is connected to a remote plasma clean (RPC) valve assembly 36 including a body 37. A valve member 38 is arranged in a valve chamber 39 of the body 37. During cleaning, RPC gas is supplied at 42 through a connector 50 to an inlet opening 54 of the valve chamber 39. If the valve member 38 is located in an open position, the RPC gas flows to a gas channel 56 that is connected to the inlet of the second gas channel 25 of the elbow connector 20 and then to the gas distribution device.
When gas is being supplied along the path 27 and the valve member 38 is in a closed position, the gas delivery assembly 10 has a dead-leg volume 60 located in the gas channel 56 and the upper portion of the second gas channel 25. The dead-leg volume 60 may trap vaporized precursor gas. The stagnant flow in the dead-leg volume may condense into particles that may fall onto the substrate, which increases defects.
Referring now to FIG. 8, another gas delivery assembly 600 is shown to include one or more valve assemblies 620-1, 620-2 . . . and 620-N (collectively valve assemblies 620) and a valve manifold 628. The valve assemblies 620 are configured to control the flow of fluid(s) into and out of the valve manifold 628. In this regard, the valve manifold 628 includes a body 674 defining one or more gas channels 676-1, 676-2 . . . and 676-N (collectively gas channels 676), first, second and third inlets 678, 680, 682, and first and second outlets 684, 685.
A first gas channel 676-1 extends from, and fluidly communicates with, the first inlet 678 of the valve manifold 628 and the second valve assembly 620-2. A second gas channel 676-2 extends from the first gas channel 676-1 to the first valve assembly 620-1. A third gas channel 676-3 extends from the first valve assembly 620-1 to the first outlet 684 of the valve manifold 628. A fourth gas channel 676-4 extends from the second valve assembly 620-2 to the second outlet 685 of the valve manifold 628.
The gas delivery assembly 600 is operated in at least three modes, such as a divert mode, a supply mode, and a standby mode. The gas delivery assembly 600 may operate in a continuous cycle such that the divert mode precedes the supply mode, the supply mode precedes the standby mode, and the standby mode precedes the divert mode. In the divert mode, stale precursor in the gas channels 676 may be replaced with fresh precursor. In the supply mode, vaporized precursor is supplied to the processing chamber. In the standby mode, vaporized precursor is not supplied and is not diverted.
When supplying vaporized precursor, the first valve assembly 620-1 is closed and the second valve assembly 620-2 is open. The vaporized precursor gas is supplied through the first gas channel 676-1 from the first inlet 678 to the second valve assembly 620-2. The vaporized precursor gas flows through the second valve assembly 620-2 and the fourth gas channel 676-4 to the processing chamber or other portion of the substrate processing system.
During the standby mode, the first and second valve assemblies 620-1, 620-2 are closed such that flow of vaporized precursor from the first inlet 678 is prevented. Accordingly, during the standby mode, vaporized precursor gas remains in the first gas channel 676-1. In some conditions, the stagnant vaporized precursor in the first gas channel 676-1 may condense into particles. Stagnant vaporized precursor that later enters the processing chamber can cause defects.
Prior to supplying vaporized precursor to the processing chamber in the supply mode, the vaporized precursor is diverted and discarded such that the stale vaporized precursor in the gas channel 676-1 is replaced by fresh precursor. When diverting the vaporized precursor, the first valve assembly 620-1 is open and the second valve assembly 620-2 is closed. When vaporized precursor gas is supplied through the first gas channel 676-1 from the first inlet 678, the vaporized precursor gas flows out of the valve manifold 628 through the second gas channel 676-2, the first valve assembly 620-1 and the third gas channel 676-3.
While the divert mode provides some improvement, not all of the stale vaporized precursor is removed. The gas delivery assembly 600 has a dead-leg volume 690 that is located downstream from the second gas channel 676-2 and upstream from the second valve assembly 620-2. Specifically, the vaporized precursor that stagnates in the dead-leg volume during the standby mode is not diverted through the first valve assembly 620-1 during the divert mode. Vaporized precursor that was trapped in the dead-leg volume 690 during the divert mode still flows into the processing chamber from the first and fourth gas channels 676-1, 676-4 during the supply mode and creates defects in the substrate.